Infatuation
by Jayalek
Summary: They came from two completley different worlds, how could they ever possibly love each other? AU NaLu! One-shot! Mermaid!Lucy


**Disclaimer: I do not own Fairy Tail.**

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 _'I'm in love with an angel, heaven forbid_  
 _Made me a believer, with the touch of her skin_

 _I'd go to hell and back with you_  
 _Still lost in what we found._  
 _Worlds apart we were the same_  
 _Until we hit the ground'_

 _ _Angel— Theory of a Deadman__

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The young prince padded out of his sleeping chambers silently, a small blue cat following closely behind. The peculiar colored feline purred, rubbing itself along its master's clothed calf. It was the middle of the night, a full moon hanged in the star filled sky, lighting his way through the dark halls. The prince padded through the corridors, not a single living thing in sight, everything deathly silent. The moon casting eery shadows, but the young man seemed undeterred. The cat, Happy, trotted ahead of him, already aware of their destination. The duo made their way through the castle silently, walking outside of the castle without hesitation without hesitation.

He was bare foot, wearing a thin dark grey night shirt and pants that hung loosely on his tall muscular form. A white scarf hung off his shoulders, he hadn't bothered to wrap the strip of cloth around his neck. His pink hair mussed from tossing and turning for hours. It was the middle of summer, hundreds fire-moths flittering around the gardens silently, like a thousand stars. Their large wings aglow with yellow light, akin to like fireflies.

The gardens of the Royal Family were known throughout the kingdom of Fiore and beyond, its beauty told in stories and legends. Most of them were true. Exotic flowers from lands across the sea, paired with other species of flower to create an intricate landscape that caught the eye. Carved stone twisting paths and jaw dropping sculptures it was truely a place to behold. It stretched on for acres, deep forests and fields of flowers, trickling rivers and even exotic birds made this garden their home.

Natsu loved the gardens, but there was one place he loved more than the sculptures and the flowers. A place he would spend hours at as a child, laughing the day away. Below him, Happy meowed up at him with those large black eyes before bounding off into the darkness, leaping into the air to try and catch a flittering moth from out of the air. The prince felt a small smile tug at his lips as he followed the feline, it was like Happy believed he had wings. His bare feet sinking into the soft wet grass as he stepped off the rocky path. Large grown trees surrounded him, with low twisting branches perfect for climbing. Long soft green grass brushed against his thighs, crickets chirping all around him.

He walked through the gardens, a set destination in mind, not even needing the light of the moon for he knew this path by heart. The fire-moths flitting around him lazily, his slitted green eyes watched a large one land gracefully onto a red rose, the flower bobbing under the sudden weight. Continuing on his way, Natsu rounded a thick tree and set eyes upon a large body of water.

The pond was beautifully simple, foliage outcropping the edges to create a suitable barrier. Large smooth rocks jutted out of the water, lillypads dotted the surface. The moon and stars shown blurrily in the reflection of the pond, ripples causing the image of the sky to become distorted. But the most beautiful part of the pond was the thousand of reflecting squirming bodies from under the surface, their vibrant scales reflecting off the full moon. Blacks, oranges, reds, whites, their scales practically glowed.

Happy crouched at the edge of the water his face mere inches from the dark depths, blue paw raised above the rippling surface as he waited for an unsuspecting fish to come to close. That cat sure did love his fish.

Natsu sighed, settling beside his cat on a smooth rock. Placing his feet into the water he watched as a few brave koi came to investigate the intrusion, nibbling on his toes. The pink haired prince smirked, wiggling said appendages, spooking the fish and making them bolt back to the masses.

The prince's green eyes scanned the water, searching for that familiar flash of gold.

"Luce, won't you come out?" Natsu spoke aloud, his voice echoeing through the silent night, a slight tease weighed down his words. A ripple went through the water, one might mistake it for a koi surfacing but Natsu knew better, a smirk spreading across his lips as his chest twisted in excitement. But soon the ripples died out and nothing else happened.

The pink haired prince sighed loudly, wiggling his toes in the water. "I know you are angry, Luce, but I miss you." He confessed softly, running his calloused fingers along the soft moss of the rocks he sat on.

Another ripple, this time a dark shadow flitted from under the surface of the water. Natsu watched unflinching as a golden crown rose from the black depths, soon followed by vibrant chocolate brown eyes glaring at him before quickly submerging back into the water with a loud splash, some of the droplets landing on him. 'How she can hold a grudge', Natsu thought.

"Luce, don't be like that." Natsu whined, kicking his feet gently in the water, making gentle sloshing sounds. "If I apologize, will you come out?" He asked, a lilt to his tone as he cocked his head, reaching over to run his fingers through the water. He was met by eery silence from the stubborn being in the water.

Natsu shook his head before he opened his mouth, "I apologize." He stated earnestly. "Now won't you come out?" Again, silence. But the shadow from under the water flitted closer; she could never stay angry at him for long.

That same golden hair escaped the dark water, followed by her glowing brown eyes, then the rest of her face. As always, she was still the most beautiful woman Natsu had ever laid eyes on. From above the surface he could make out where her torso transformed into beautiful black and gold scales that created amazingly stunning designs along the length of the long flowing tail that flittered back and forth to keep her steady. Long thin gold black fins moved lazily though the dark water. Lucy herself held a certain exotic aura that always drew him towards her, but Natsu knew that had to do with the fact that she was a siren. If she ever decided to sing to him, Natsu would walk right into the dark depths to his death without a care.

But Lucy was the most docile siren that lived in his family's garden. He wasn't to sure if Aquarius wouldn't pass up the opportunity to have pink-haired-prince as a midnight snack though. Beside him, Happy mrowed happily at the sight of Lucy, a purr vibrating in his chest as he took a lithe step into the cool water. Happy was the only cat Natsu had seen to willingly step into water, he even swam sometimes.

Lucy's gaze went from Natsu to Happy, a smile spread across her beautiful face at the sight of the cat. Swimming closer she lifted a hand to let the blue furred feline. A thin webbing connected each of her long fingers, gold and black scales dotted her shoulders and neck. Her webbed hand ran along Happy's fur, getting him all wet. But the cat didn't seem to care as he leaned into Lucy's touch with another loud purr.

"Happy missed you too." Natsu spoke finally. Lucy's eyes looked up at Natsu and she snorted at him, a series of strange clicks escaped her chest. Since sirens had delicate vocal cords, only used when hunting, they communicated with others by clicking. Almost like Morse code, yet way more elaborate. Natsu was able to understand the bare minimum of her language, even after all the years of playing with her.

The best Natsu could translate was that she had missed Happy too. The small cat had been introduced to Lucy when he was just a kitten four years back, the siren had been smitten by the small feline, clicking loudly with excitement as she stroked his downy kitten fur in amazement. She had immediately introduced him to the water, nearly giving a fifteen year old Natsu a heart attack. But Lucy was careful not to let the kittens head under the water, knowing that this creature wasn't like her and couldn't live in water. Perhaps that was why Happy liked water so much. Sometimes the feline would leap right in to go find Lucy, which Natsu found adorable.

Natsu came to the pond whenever his schedule allowed, telling Lucy everything about his day, which girls he had a crush on, how his brother and parents were doing, everything. Sharing his darkest secrets, or just enjoying her peaceful company. When he couldn't sleep, he would come down to visit her, like right now. She always listened, even if she didn't understand some of his words. And he, in turn, would listen to her. Faint scraps of understanding would leak through when she told him things. But Natsu did his best to listen and understand like she did for him.

On hot days, Natsu would play in the water with her, she would travel up the stream to a larger body of water that didn't have as many koi. Aquarius wasn't there either so he could jump in the water safely and they would swim the day away. Lucy had to save him from Aquarius' song twice in the time that he had known her. Though his father assured him that Aquarius was just being cranky and wouldn't dare hurt a member of the royal family, Natsu had always been wary of the blue haired siren.

There were other mermaids in the garden, they came up to the surface when he visited sometimes. Juvia was yet another blue haired siren, with a long blue tail; she had an odd demeanor and was prone to a quick change in attitude. She was infatuated with a dear friend of Natsu's, Gray Fullbuster, who was a prince in an allied nation that would visit in the spring. Lucy had told him so and was then hit by a mysterious ball of water in the face, much to her chagrin.

Then Erza, with crimson red hair, her tail was a mixture of black and red; Natsu swore she was almost as scary as Aquarius at times. Levy was a much smaller than her comrades; he had only seen her a couple times, always prodded by Lucy to meet him. Then the last one was Mavis, another blonde siren who was very clever, she and Aquarius were the only two who could speak words of English though just barely. He would sometimes catch his brother, Zeref sneaking down to go see her as well.

He would sometimes see his blonde siren playing with the rest them, excluding Aquarius, jumping and swimming with a large smile on her angelic face as she spoke to them in that strange language of hers. He had once seen Juvia control the water, creating a bubble of water above the pond with Lucy and a dozen koi caught inside. When questioned, and after many repeats of the same sentence, she told Natsu she had wanted to see the Rainbow Sakuras' bloom and Juvia had offered to help. So, Natsu had ordered to have the largest Rainbow Sakura to be replanted right next to the pond so she could see it every single year up close. Her excited clicks of gratitude and sunny smile were enough for him.

Lucy let go of Happy and placed him back on the shore where the blue cat sat down and began to lick the water off of himself. Natsu watched as she raised herslef farther out of the water, a black swimsuit like top covered her rather generous chest. The gold scales that dotted her shoulders glistened in the light of the moon.

"I really am sorry, Luce." Natsu stated with a frown. Lucy didn't say anything, simply stared at him with those mesmerizing brown eyes. They stared at each other for a few moments before the siren's face relaxed and she huffed, a series of clicks echoeing from her chest in exasperation as she averted her gaze, cheeks flushed. Natsu felt relief flow through him now that she had forgiven him.

He watched as she lifted a webbed hand to touch his own larger one delicately. Grabbing his wrist gently she lifted it up and began to play with his hand absentmindedly. She always liked to mess with his limbs, especially his feet. The siren found them so incredibly odd that she always played with his toes. It used to be weird, but now Natsu found her curiosity endearing.

Lucy clicked again, not looking up as she messed with his fingers; Natsu had to pause for a second thinking before he figured out what she said. ' _How is Natsu's brother?_ '

"Zeref is doing well, father is about ready to give him the title of king." He told her slowly so she could understand.

' _Does this bother Natsu?'_

"Eh, not really. It used to, but now... I think I've excepted that I won't be king. I really don't want to be anymore anyways, to much stress." Natsu answered.

' _Mavis fancies Zeref, you know_.' She stated absentmindedly, tracing a scar on his forearm with cool fingers. Natsu smiled at her words "I've suspected."

Lucy stared up at him questioningly, gesturing that she did not know what 'suspected' meant. Their conversations were always slow going, but they were no less entertaining. "Suspected is...it's like guessing that something will happen." Natsu told her. Lucy nodded her understanding, placing their hands together. His own hand was larger than hers, much darker than her pale skin as well.

"Enough about me, how's the rest of the sirens?" Natsu asked, leaning forward.

' _Erza is being weird_.'

Natsu laughed good naturedly, a smile spread across his face at his dear friends bluntness. "How so?"

 _'I believe she met someone two moons back.'_ Lucy told him, a mischievous glint in her eye. ' _She is also infatuated with someone, I think._ ' She stated, remembering just yesterday she had seen the red head watching a blue haired knight with a strange marking around his right eye walk through the garden with a look of admiration in her red eyes.

It pained Natsu to know that the relationships the sirens and secretly he himself chased was nigh impossible. They lived in completley different worlds, they could barely understand each other at all. It would be nearly impossible for a relationship like that to work at all, and that thought pained him greatly.

"And you? Are you...infatuated with someone, Luce?" Natsu asked, holding his breath as he watched the blonde let go of his hand and let out a long sigh. Her cheeks tinted pink adorably as she thought over whether to tell him or not.

She took a deep breath, swimming closer she placed herself in between his legs, using his knees to pull herself up to eye level to get close to his face. "Natsu..." Lucy whispered, a singing lilt to her voice to make it easier on her vocal cords. His eyes widened in shock as he spoke his language. Over all the years he had known her she had never even attempted to speak, it obviously hurt her throat to do so and he watched in amazement as she opened her mouth to speak again.

"I...love...you." She stated, staring him right in the eye. Natsu had no idea what to say or do, he stared at the siren for a long moment in complete shock. Lucy's heart clenched in panic, had she said those words wrong? She was sure she hadn't. Natsu had explained to her what love was before, when she inquired about it after he read her a romance novel. Lucy's face fell as he just stared at her with an unreadable expression, maybe she had misread his body language all this time and he in fact didn't share the same feelings. Letting out a shaky breath she began to lower herself back into the water to swim away to the darkest corners of the pond and never resurface.

She was shocked to feel his hand on her scaled shoulder, pulling her back to him, her brown eyes widening at the feel of his warm lips on her cool ones. It was her turn to be shocked, the meaning behind this gesture not lost on her. She knew what a kiss meant to humans, and her heart fluttered inside her chest at the notion her prince bestowed on her. She quickly returned the gentle kiss, not quite sure on what to do. Lucy was not sure whether to be relieved that it was over so she couldn't embarrass herself, or sad that it was _over_.

"I love you too, Luce."

No matter how impossible this relationship may be, Natsu was willing to try his hardest to make it work.

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 **AN: Okay so this is my first time doing a one-shot like...ever! I started writing this at two o'clock last night because I couldn't sleep and finished it this morning. This was really fun to write, it was especially cool to do an AU, I have never done one of those before either. So, this was actually a lot of fun and was a lot of firsts for me, so I hope I did good...**

 **I got this idea when I read the newest chapter of Fairy Tail last week where Lucy gets temporarily turned into a mermaid along with Brandish for like five minutes. I just never really thought I would actually write it xD. But I was bored last night, and it was a Friday (well Saturday) and I did not feel like working on any of my other stories. So I wrote something new!**

 **On why Lucy is upset with Natsu... Use your imagination!**

 **Hope you guys like it! Tell me what you thought!**


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